The present invention relates to land grid arrays, and more specifically, the invention relates to a removable land grid array cooling solution assembly and a method of assembling the same.
Electronic components such as modules are often permanently soldered to a circuit board. In contrast, a land grid array (LGA) module is socketed to the circuit board through an area array connector. Socketing of modules in a LGA assembly provides many advantages, among them field upgradability, flexibility in the system bring-up and diagnosis, reduced board assembly rework cost, reduced effects of thermal mismatch between module and board, improved electrical performance, and an adaptability to compact mechanical designs.
As shown in FIGS. 1 and 2, current applications of LGA assemblies 10 may include a cooling solution 11 such as a heatsink, heatpipe, fansink, or coldplate disposed on a module 13. The cooling solution 11 has two functions: to serve as the heat dissipation medium, and to serve as one of the structural load plates that is required for making the electrical connection. An area array connector device provides an electrical connection between mating surfaces of the module 13 and a printed circuit board 15 through a conductive interposer 14 that is compressed between the module 13 and the board 15. The LGA assembly 10 also includes a backside mount comprising: an insulator 16, a backside stiffener 17, a springplate assembly with threaded bushing 18, and a load screw 19. The backside mount is attached to cooling solution 11 via load posts 12, which engages keyhole features in the springplate 18. Turning the load screw 19 develops a compressive force within the assembly 10. The compressive force maintains the electrical connection between the module 13 and the board 15.
Removal of the cooling solution 11 is accomplished by loosening the load screw 19, disengaging the load posts 12 from the springplate 18 keyhole features, and pulling the cooling solution 11 and load posts 12 from the assembly 10. This action not only removes the cooling solution 11 but also breaks the electrical connection of the socket. Furthermore, removal of the cooling solution 11 may cause the module 13, interposer 14, insulator 16, backside stiffener 17, and springplate 18 to become loose and unconstrained parts.
One shortcoming of the current designs is that when the cooling solution is removed from the LGA assembly, the electrical connection is broken. This is disadvantageous because subsequent reassembly may result in a bad connection due to improper reloading or alignment of the electrical connection, introduction of contamination into the connection, and increased wear of the connection due to repeated assembly-disassembly. The cooling solution may need to be removed and replaced without breaking the electrical connection due to a need to test the card in a development or manufacturing environment with an alternative cooling scheme different from that employed on the actual product. Other reasons for cooling solution removal and/or replacement include failure of the cooling solution on a functional card and shipment and/or stocking of fully functional cards without the cooling solution.
Another shortcoming of the current designs relates to occasions when the cooling solution may not be removed from the system. Fixed cooling solutions include those employing liquid or refrigeration cooling assemblies that circulate a thermal fluid through pipes/hoses to coldplates attached to the modules to be cooled. It would be desirable, then, to allow for functional cards to be moved from slot to slot within a given machine or from machine to machine without breaking the electrical connection or disrupting the fixed cooling solution. Additionally, failed cards could be removed from the system and analyzed with an intact electrical connection.
In summary, socketing of modules in LGA assemblies provides many advantages including upgradability, flexibility, reduced cost and thermal mismatch, and improved system performance and adaptability. The current assembly designs, however, prohibit the cooling solution from being removed without breaking the electrical connection between the module and the circuit board. Therefore, it would be desirable to achieve a LGA assembly capable of repeated cooling solution assembly-disassembly without disruption of the module-board electrical connection. The novel LGA assembly should overcome the aforementioned and other disadvantages.
One aspect of the invention provides a land grid array cooling assembly comprising: a card, a module electrically connected to the card, a plurality of load posts operably attached to the card, a load frame operably attached to the load posts, and a cooling member operably attached to the load frame to allow removal of the cooling member from the assembly without disrupting the electrical connection between the module and the card. A backside mount may be positioned adjacent the card, wherein the backside mount may be operably attached to the load posts. An area array connector may be positioned between the card and the module wherein the area array connector may provide an electrical connection between the card and the module. The electrical connection may comprise a socket connection. The cooling member may be any thermal solution, including a heatsink, a heatpipe, a fansink, or a coldplate. At least one bolt may operably attach the cooling member to the load frame. A clip may operably attach the cooling member to the load frame. The load frame may facilitate a thermal transfer between the module and the cooling member. The load frame may provide a load force onto the module thereby maintaining the electrical connection between the card and the module.
Another aspect of the invention provides a method of assembling a land grid array cooling member assembly comprising: electrically connecting a module and a card, operably connecting a load frame to the card, and removably attaching a cooling member to the load frame without affecting the electrical connection between the module and the card. An area array connector may be positioned between the card and the module. An electrical connection may be provided between the card and the module with the area array connector. The electrical connection may comprise a socket connection. A backside mount may be positioned adjacent the card. The backside mount may be operably attached to the load frame. Operably attaching the backside mount to the load frame may produce the electrical connection between the module and the card. The cooling member may be any thermal solution, including a heatsink, a heatpipe, a fansink, or a coldplate. The cooling member may be operably attached to the load frame with at least one bolt. The cooling member may be clipped to the load frame. A thermal transfer may be provided between the module and the cooling member. A load force may be provided onto the module, and the electrical connection between the card and the module may be maintained.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.